Tumultuous is an adjective that is used to describe a situation that is loud, confused, and often violent or chaotic. However, there are several antonyms for tumultuous that describe the opposite of chaos or commotion. Some possible antonyms for tumultuous include calm, peaceful, placid, tranquil, and serene. A calm environment, for instance, refers to a place that is free from disorder or agitation. Similarly, the word peaceful connotes a state of harmony and tranquility, while placid suggests a state of quietness or calmness that is undisturbed by external stimuli. On the other hand, serene describes a state of complete calmness and tranquility, and it is often used in relation to nature or scenic beauty.